632 GEOLOGY OF OHIO. 
The material is chiefly used for foundations and bridge work, and 
was largely employed in the construction of the depots and shops of the 
Columbus and Hocking Valley railroad. It is commonly called blue 
limestone, although the colors differ at different horizons, and the layers 
also vary in texture and hardness, each layer, however, being homo- 
geneous. ‘The stone is usually quite fine in grain and rather hard. The 
following may be regarded as a typical section representing this and all | 
other quarries in the neighborhood of Marion: 
Feet 
SOUL ccccesesecstestevssaleceeusveceadacacsbcecenesee seen tne tee seen ERROR Lan aanen 1 to 4 
Weathered wroelkk ac2essickee teresa te tetas ethos ee ee 1 to 4 
IBIAVESSLONE o54 cy sBiscocsalssedbesos cost duenseen cement etak SERRE ee ee 1 to 6 
GLAYASLOMC oo vacies van ieee v's heasasbscie sree call aeeeeneetacauk seeteceecse OCR enna 4 
DBO SEO Gioia ve cee esoc see ceiscs ee US Ree See Cea ee ee eS Ce TSS Ee ee EE 
The overlying blue-stone is found in blocks from the exterior of 
which a gray color penetrates to a variable depth from the natural 
joints. It is liable to contain flinty nodules, from which the under- 
lying gray-stone is almost entirely free. The blue-stone in the bottom 
ofthe quarry is free from this gray covering; but the intermediate stone, 
which is all gray, is considered the best material. 
In these quarries the gray-stone is found near the top, but in the 
other quarries reported from this township, being about ig miles to the 
southeast of these, and in the direction of the dip of the strata, this gray 
layer is not struck until a depth of from 12 to 16 feet from the surface is 
obtained. A very large amount of the cap-rock has been used for 
macadamizing streets and for ballast on the Columbus and Toledo rail- 
road. ‘The quarries in this township furnish the greater part of the 
stone used in the northern part of Union county and in quite a large 
portion of Hardin county. 
The material quarried at Marion is dolomite, containing some calcite. 
When microscopically examined it is found to consist of a multitude of 
perfect little rhombohedral crystals, each one of which contains a little 
black bituminous substance accumulated in its center, and all are 
cemented together by the calcite, which, although crystalline, does not 
assume a definite outline. The rock, when treated with cold and dilute 
acid, effervesces for a while, and the residue when examined is found to 
consist of a multitude of perfect and beautiful little rhombohedrons. 
The Marion stone has been selected for representation in the plate of 
